1. Field of the Invention
The present invention relates generally to Coriolis type mass flowmeters, and more particularly to an improved enclosure for such a device that, in interacting with the surrounding thermal, stress, and vibrational environments, does not affect operation of the meter.
2. Brief Description of the Prior Art
Coriolis-effect type mass flow rate meters are well known in the prior art and provide an accurate and efficient means of determining the mass flow rate of fluids and/or liquid-solid slurries flowing through a pipeline or conduit. Coriolis mass flowmeters are typically shielded from the ambient environment, corrosives, etc. by an enclosure. Such flowmeter enclosures are typically fabricated from sheet metal (or other suitable material) that is welded, or otherwise securely attached, to the meter support.
As depicted in FIG. 1 which illustrates at 10 a Coriolis flowmeter apparatus including a flowmeter shown generally at 12 and an enclosure 14, fluid passes through the flowmeter 12 in a direction as illustrated by arrows 13 and 15. The apparatus includes an input flange 16, an input conduit 17, the flowmeter metering section 12, a support bracket 13, an output conduit 19, and an output flange 18. The enclosure 14 includes an upstream endcap 22, a downstream endcap 24, and a sleeve 26 which is welded or otherwise affixed to the bracket 13 a suggested at 27.
The endcaps 22 and 24 are welded or otherwise rigidly secured to the sleeve 14. The endcaps are also rigidly secured to the inlet and outlet conduits by means of nipples 28 and 29 which are welded or brazed thereto. The necessary electronics for monitoring the vibrations and for driving the conduit sections are not shown.
There are several problems encountered with the enclosure 14 associated with the Coriolis flowmeter 12. First, pipeline vibrations can excite the enclosure 14 which, in turn, interacts vibrationally with the metering section, causing flow measurement errors.
A second problem is that axial stresses may be caused by changes in fluid temperature, changes in ambient temperature, and the differential thermal expansion of the enclosure sleeve 14 relative to the metering section and support bracket. These stresses adversely change the vibrational characteristics of the flowmeter and its enclosure, thereby causing flow measurement errors.
Transverse and axial stress loadings may also be impressed on the metering section from mechanical stresses resulting from the mechanical mounting of the apparatus to the pipeline. These stresses can alter the modal vibration characteristics of the enclosure 14 with the result that the enclosure adversely interacts with the sensitive portion of the metering assembly, thereby causing mass flow measurement and zero offset errors.
While it may be difficult to completely eliminate such detrimental influences, problems associated with the interaction between the sensitive portion of the metering assembly and its surrounding enclosure can be improved in accordance with the present invention.